Malaria is currently ranked as one of the most deadly human infectious diseases, causing an estimated three million deaths each year with half of these being children under the age of 5 years. Approximately 500 million people are currently infected with one or more species of Plasmodium, with 90% of the infections occurring in sub-Saharan Africa. In regions of the highest endemicity, a significant level of malaria transmission is vectored by the anthropophilic mosquito An. gambiae sensu stricto Giles. Using molecular techniques, native An. gambiae s.s. carboxypeptidase A, a secondary digestive enzyme that breaks down bloodmeal proteins required for egg production, was isolated and two recombinant forms were produced. These proteins were used as antigens in phage display panning to isolate humanised antibodies with high affinity to the enzyme. Two of these phage antibodies, A7 and B10, were used in in vitro assays and in vivo feeding studies. Neither antibody produced enzyme activity in vitro, but A7, which bind specifically to the active site region of the mosquito carboxypeptidase A, affected longevity, egg development, and F1 generation viability. B10, binding outside of the active site region, generally responded in the same patterns as the PBS control. A potential detrimental factor in the in vivo studies was the probable toxicity of imidazole, an eluate solution used in phage display, which may have contributed to the mortality rate of mosquitoes in the A7 and B10 treatment groups. These results have contributed to the redesign of the phage display protocol for use in n vivo mosquito systems.